1. Field of the Invention
The present invention relates to a vehicular radar device having a radar to be mounted on a vehicle, which detects an object existing in the periphery of a subject vehicle (hereinafter, referred to as “target”) and measures a position and a velocity of the target, and more particularly, to a vehicular radar device which is capable of estimating and correcting a reference axis deviation angle (hereinafter, referred to as “axis deviation angle”) of a radar measurement coordinate system.
2. Description of the Related Art
When the vehicular radar is mounted on a vehicle, due to various factors, a vehicle forward direction may be deviated from the reference axis of the measurement coordinate system of the radar as illustrated in axis deviation examples I and II with respect to an ideal state, as illustrated in FIG. 3. With this deviation, a relative position of a peripheral target with respect to a traveling subject vehicle cannot be obtained.
As a method of detecting the axis deviation angle of the vehicular radar, there is a conventional art using the following principle Expression (1) that is satisfied by an azimuth angle θ and a relative Doppler velocity Vs which are measured with respect to the target, a travel speed Vh of the subject vehicle, a velocity error ratio A included in the relative Doppler velocity Vs and the travel speed Vh of the subject velocity, and an axis deviation angle ψ (see, for example, JP 2002-228749 A).
                    [                  Equation          ⁢                                          ⁢          1                ]                                                                                  V            s                                V            h                          =                  A          ·                      cos            ⁡                          (                              θ                +                ψ                            )                                                          (        1        )            
However, the related art suffers from such a problem that not only the axis deviation angle ψ but also the velocity error ratio A must be estimated, and a large number of operation resources are required for an estimating process, which increases the device size, for example.